This invention relates to the insertion of an elongated member, such as a catheter, into a body and, more particularly, to an improved device for both dilating a puncture hole in the body and for subsequently providing a guide for the insertion of an elongated member into the body through the puncture hole.
In the following discussion, specific reference will be made to inserting a catheter into a blood vessel. However, it will be appreciated that similar problems arise when inserting other elongated members into a body. Thus, guidewires, optical fibers, stents, etc., are often inserted into a body by forming a puncture hole and guiding such a member into the body through the puncture hole. Accordingly, the present invention has been developed to aid in the insertion of any such elongated member into a body, and use of the term "catheter" is intended to cover all such elongated members.
Vascular dilators are commonly used when inserting a catheter into a blood vessel in order to widen the hole formed by the initial needle or scalpel puncture so that the use of the dilator gradually enlarges the hole. In a typical procedure, a hollow needle is percutaneously inserted into the blood vessel and an elongate, slender guide member, such as a guidewire, is advanced through the interior of the hollow needle into the blood vessel. The needle is then removed over the guide member, leaving the guide member in place in the blood vessel and extending proximally out of and through the patient's skin. The hole left by the needle in the blood vessel typically is too small to permit the catheter to be passed therethrough. A dilator is provided to widen the hole. Dilators commonly are in the form of a flexible plastic tube having a guide member lumen adapted to be passed over the guide member. The dilator is of uniform wall thickness except for a distal portion which tapers in a distal direction to the circular distal outlet opening at the distal end of the dilator. The wall thickness of the dilator at the distal tip is relatively thin to facilitate its entry into the hole made by the needle. As the dilator is advanced over the guide member through the puncture hole, the tapered distal portion presents a progressively wider diameter to the puncture hole, thus gradually enlarging the hole. The dilator is then removed and the catheter is advanced over the guidewire and through the enlarged puncture hole into the blood vessel. The guide member is then withdrawn, leaving the percutaneously placed catheter in place in the blood vessel. This procedure possesses a number of disadvantages. For example, to accommodate the guide member, a relatively large needle is required to penetrate the wall of the blood vessel. Also, a disposable guide member is required.
It would therefore be desirable to provide a catheterization device wherein only a relatively small diameter needle is utilized and no separate guide member is needed.